Metallic contaminant was found in the liquid oxygen (LOX) pre-valve screen of the shuttle main engine propulsion system on two orbiter vehicles. To investigate the potential for an ignition, NASA Johnson Space Center White Sands Test Facility performed (modified) rotating friction ignition testing in LOX. This testing simulated a contaminant particle in the low-pressure oxygen turbo pump (LPOTP) and the high-pressure oxygen turbo pump (HPOTP) of the shuttle main propulsion system. Monel® K-500 and Inconel® 718 samples represented the LPOTP and HPOTP materials. Aluminum foil tape and titanium foil represented the contaminant particles. In both the Monel® and Inconel® material configurations, the aluminum foil tape samples did not ignite after 30 s of rubbing. In contrast, all of the titanium foil samples ignited regardless of the rubbing duration or material configuration. However, the titanium foil ignitions did not propagate to the Monel and Inconel materials. Based on these results, NASA determined that the risk of a fire occurring in the turbo pumps was acceptably low.

Author Title Liquid Oxygen Rotating Friction Ignition Testing of Aluminum and Titanium with Monel® and Inconel® for Rocket Engine Propulsion System Contamination InvestigationSymposium Twelfth International Symposium on Flammability and Sensitivity of Materials in Oxygen-Enriched Atmospheres, 2009-10-09Committee G04